chat: fix jinja parser for TranslateGemma (#30096)

* chat: fix jinja parser for translategemma

* log if missing soruce_lang_code or target_lang_code

common/chat.cpp

@@ -1223,6 +1223,13 @@ std::optional<common_chat_params> common_chat_try_specialized_template(
         return common_chat_params_init_minicpm5(tmpl, params);
     }
 
+    // TranslateGemma - user content must follow a custom schema with language codes
+    if (src.find("[source_lang_code]") != std::string::npos &&
+        src.find("[target_lang_code]") != std::string::npos) {
+        LOG_DBG("Using specialized template: TranslateGemma\n");
+        return common_chat_params_init_translate_gemma(tmpl, params);
+    }
+
     // Qwen3-Coder XML tool calls, also used by Nemotron Nano 3, Qwen3.5 and StepFun-3.5-Flash
     if (src.find("<tool_call>") != std::string::npos &&
         src.find("<function=") != std::string::npos &&